1. Field of the Invention
The present invention relates to a data reading and writing apparatus such as a camera capable of magnetic recording, and more specifically, to a camera capable of magnetic recording which uses film having a magnetic recording portion.
2. Description of the Prior Art
A data reading and writing apparatus such as a camera capable of writing data associated with photographing (e.g. the photographic mode, the number of prints, the shutter speed and the aperture value, hereinafter sometimes referred to as "photographic data") onto a magnetic recording portion provided on film is disclosed by U.S. Pat. No. 4,860,037. The data magnetically recorded on the magnetic recording portion of the film are read out in a laboratory. The photos are printed in accordance with the data.
However, since the data recorded onto the magnetic recording portion by this camera are recorded while the film is being wound or rewound, there are occasions when the data are not normally recorded due to the nonuniformity of film transportation speed caused by variation in battery voltage and the wow-flutter of film transportation caused by low mechanical precision. Therefore, the recording condition of the data written on the magnetic recording portion is not very excellent.
Data readers used in laboratories are designed to be able to read out such abnormally recorded data. However, in order that such abnormally recorded data are normally read out by household readers (such as an apparatus for displaying an image on film on the TV), it is necessary for the household readers to have a data reading performance equal to that of the readers used in laboratories. As a result, the cost of the readers increases.
In digital-recording data, an error correction code is usually added to the data. When the data are read out by using the error correction code, the data can be normally read out even though the signals are partly lost due to drop out. However, if the signal loss increases, it will be impossible to normally read out the data.
Moreover, in the camera of the U.S. Patent, when a user takes a photo believing that the camera is in the normal mode although it is actually in the panorama mode, the data recorded on the magnetic recording portion (hereinafter sometimes referred to as "magnetic data") cannot be changed even though the user notices the error. Moreover, when the number of prints is mis-set, an unnecessary number of pictures are printed.
Japanese Laid-open Patent Application No. H4-349448 proposes a magnetic recorder which modifies photographic data of developed film. This recorder is designed to modify the magnetic data by setting the trimming magnification and date of a frame to be modified and writing them onto the magnetic recording portion of the film.
However, since the magnetic recorder of Japanese Laid-open Patent Application No. H4-349448 is for developed film, the magnetic data cannot be changed before development. Therefore, the photos must be printed even if it is unnecessary.